Conferencing environments, such as boardrooms, video conferencing settings, and the like, can involve the use of microphones for capturing sound from audio sources. The audio sources may include human speakers, for example. The captured sound may be disseminated to an audience through loudspeakers in the environment, a telecast, a webcast, telephony, etc. The types of microphones and their placement in a particular environment may depend on the locations of the audio sources, physical space requirements, aesthetics, room layout, and/or other considerations. For example, in some environments, the microphones may be placed on a table or lectern near the audio sources. In other environments, the microphones may be mounted overhead to capture the sound from the entire room, for example. Accordingly, microphones are available in a variety of sizes, form factors, mounting options, and wiring options to suit the needs of particular environments.
The types of microphones that can be used for conferencing may include boundary microphones and button microphones that can be positioned on or in a surface (e.g., a table). Such microphones may include multiple cartridges so that the microphones have multiple independent polar patterns to capture sound from multiple audio sources, such as two cartridges in a single microphone for forming two separate polar patterns to capture sound from speakers on opposite sides of a table. Other such microphones may include multiple cartridges so that various polar patterns can be formed by processing the audio signals from each cartridge. These types of microphones are versatile since they are configurable to form different polar patterns as desired without the need to physically swap cartridges. For these types of microphones, while it would be ideal to co-locate the multiple cartridges within the microphone so that each cartridge detects sounds in the environment at the same instant, however, it is not physically possible. As such, these types of microphones may not uniformly form the desired polar patterns and may not ideally capture sound due to frequency response irregularities, and interference and reflections within and between the cartridges.
Typical polar patterns for microphones and individual microphone cartridges can include omnidirectional, cardioid, subcardioid, supercardioid, hypercardioid, and bidirectional. The polar pattern chosen for a particular microphone or cartridge may be dependent on where the audio source is located, the desire to exclude unwanted noises, and/or other considerations. In conferencing environments, it may be desirable for a microphone to have a toroidal polar pattern that is omnidirectional in the plane of the microphone with a null in the axis perpendicular to that plane. For example, a microphone with a toroidal polar pattern that is positioned on a table detects sound in all directions along the plane of the table but minimizes the detection of sound above the microphone, e.g., towards the ceiling above the table. However, existing microphones with toroidal polar patterns may be physically large, have a high self-noise, require complex processing, and/or have inconsistent polar patterns over a full frequency range, e.g., 100 Hz to 10 kHz.
Accordingly, there is an opportunity for microphones that address these concerns. More particularly, there is an opportunity for microphones including multiple unidirectional microphone cartridges that can reduce interference between the cartridges, more uniformly form desired polar patterns, form a toroidal polar pattern, are relatively small and compact, and have a relatively low self-noise.